\documentclass{ctexart}
\usepackage{avanti}
\everymath{\color{Solarized-magenta}}
\pagestyle{empty} % 没有页眉和页脚

 % define the plot style and the axis style
\tikzset{base/.style={smooth,thick,Solarized-base01}}
\tikzset{arrow/.style={->,>=stealth,base}}

\begin{document}

\begin{figure}[!ht]
    \centering
    \begin{tikzpicture}

        \draw[arrow] (0,0) -- (8.5,0) node[below] {};
        \draw[arrow] (0,0) -- (0,5) node[below] {};

        \draw[base,Solarized-yellow,domain=0.5:6.5] plot(\x,{0.08*(\x-0.2)^2+0.2});
        \draw[base,Solarized-blue,domain=0.5:6.5] plot(\x,{0.08*(\x-6.8)^2+0.2});
        \draw[base,Solarized-red,domain=0.5:6.5] plot(\x,{0.3*(\x-3.5)^2+2});

        \path (7.4, 0.3) node[Solarized-blue] () {经验风险};

        \path (7.4, 3.4) node[Solarized-yellow] () {置信区间};

        \path (7.4, 4.6) node[Solarized-red] () {泛化风险};

        \path (7.95, -0.3) node[Solarized-base01] () {VC维};

    \end{tikzpicture}
\end{figure}


\end{document}